Piston



FIG. 1 is a perspective view of the piston;

FIG. 2 is a front view of the piston looking along a pin bore axis;

FIG. 3 is side view of the piston looking transverse to the pin bore axis;

FIG. 4 is a top view of the piston; and,

FIG. 5 is a bottom view of the piston. 

CLAIM I claim the ornamental design for a piston, as shown and described. 